A hybrid density functional study of tensile-induced changes in phonon dispersion, electronic structure and optical absorption of bilayer BN for optoelectronic applications

The electronic, phonon dispersion and optical properties of bilayer BN have been investigated with density functional theory (DFT) calculations. Interestingly, applying the biaxial strain of 4% converts the indirect band gap of bilayer BN to a direct band gap. The interlayer coupling in bilayer BN causes the splitting of out-of-plane ZA and ZO modes at the Γ point. For all applied biaxial tensile strains, positive phonon modes have been observed which demonstrate the dynamical stability of the bilayer BN under biaxial tensile strain. The phonon bandgap of bilayer BN decreases under tensile strain. The bilayer BN has strong adsorption in the UV region and the optical absorption peaks are red-shifted by applying the tensile strain. These results demonstrate that the phonon dispersion and electro-optical properties of bilayer BN could as well be tuned with biaxial strain that are promising for optoelectronic applications.